Scientific sleuths tail bay invaders

EDGEWATER — EDGEWATER -- Greg Ruiz uses a pair of tweezers, tugging flesh out of the leg of a curiously hairy crab and thrusting it into a plastic vial.

Ruiz, director of the Marine Invasions Research Lab, packs the vial into a blue plastic box, which he will ship off for DNA analysis to determine where the crab came from. Then he aims his pincers at his next subject - one of six Chinese mitten crabs spread out on his lab table.


Ruiz is like a detective. He's trying to solve the mystery of how this spider-like Asian creature started breeding in the Chesapeake Bay and whether it's likely to threaten blue crabs or other native species.

He and other researchers in the lab, part of the Smithsonian Environmental Research Center, have found an increasing number of foreign organisms establishing themselves in the Chesapeake Bay in recent years. An estimated 175 alien species are now thriving in the bay's tidal waters, about 20 of which have been detected in the last decade.


Many have been carried in ballast water or on the hulls of ships as globalization has increased trade. The Internet has also spurred cross-border sales of exotic pets and other animals for ethnic food, some of which are dumped in the bay.

In addition to the Chinese mitten crabs, the most recent invaders have included snakeheads from China (2004), crayfish leeches from the Mississippi (2003), and marine sowbugs (2002) and sea squirts (2002), both from the Pacific Ocean.

"It's not just mitten crabs - that's just one of a whole series of new species that are showing up in the bay," said Ruiz, a biologist, poking at the fuzz on a mitten crab's claw. "They're a symptom of a broader pattern - the door is open, new species are coming in, and we are trying to explore what impact they might have."

Most exotic species that try to reproduce in the Land of Pleasant Living find it unwelcoming. Most perish, a few become established without much notice, and about 1 percent thrive and cause serious problems, said Paul Fofonoff, a biologist in the lab.

Perhaps the worst damage was caused by the invasive parasite MSX, a protozoan that has decimated native oyster populations in the Chesapeake. It was probably introduced to the region during the 1950s, carried inside Asian oysters that researchers were trying to farm in Delaware and Chesapeake bays, Fofonoff said.

Many more resident aliens are ignored or accepted as normal or even desirable - such the largemouth bass. This voracious predator was introduced to the Potomac River from the Great Lakes about 1876 and likely killed some native striped bass, but it is now a highly popular sport fish.

Trying to find invaders is not a form of xenophobia, Ruiz points out. It's economically smart because keeping out aggressive aliens like MSX can potentially save local fisheries. Beyond business concerns, the spread of invasive species could leave the world with a few dominant species that kill off competitors, leaving a planet with less biological diversity.

"Some people may not care if there are mitten crabs here, but some of these invaders can have huge impacts - environmentally and economically," Ruiz said.


For the last 15 years, Ruiz has been running the Marine Invasions Research Lab in a low-slung building on the Smithsonian's sprawling 2,800-acre campus beside the Rhode River south of Annapolis.

He leads a team of 25 researchers in an office crowded with microscopes, three-ring binders and jars holding specimen.

A colleague jokes that Ruiz and his sidekicks are like the agents in Men in Black, the 1997 movie about government investigators in dark glasses who hunt down aliens from outer space that menace the Earth. But Ruiz doesn't look much like Will Smith. The 49-year-old with a doctorate in zoology wears wire-rimmed glasses, jeans and sandals.

His main weapons are microscopes and bricks. He lowers the bricks from docks to see if any foreign creatures cling to them, evidence that the pests are hitching rides into harbors on boats. He then uses microscopes, computer databases and such techniques as DNA testing to determine where the species came from.

His lab's research has concluded that some simple techniques are extremely effective at halting marine invaders. For example, forcing ships from Asia and elsewhere to dump their ballast water in the open ocean, instead of carrying it into the bay, prevents millions of exotic eggs and larvae from being introduced, Ruiz said.

"We should be thinking about how these things are arriving to prevent the next mitten crab from showing up," Ruiz said.


Chinese mitten crabs have been a focus of the lab since last August, when a waterman checking his crab pots in the Patapsco River south of Baltimore pulled up what looked like a hairy daddy longlegs.

After consultation with a Chinese biologist, Ruiz concluded it was a Chinese mitten crab, a species that has hitchhiked in ships to colonize in Germany, England, San Francisco and elsewhere. They are considered a potential threat because they sometimes explode in population to such an extent that they compete with local marine life and dig burrows that erode riverbanks and dams.

Ruiz's lab worked with the Maryland Department of Natural Resources and other government agencies to alert local watermen. Over the last year, the alert has prompted about 100 people to call a "mitten crab hot line."

Most of the calls have been false alarms - a few for things even stranger than the furry-cuffed mitten crabs. On July 7, officials at Sandy Point State Park near Annapolis called to report finding a rainbow-hued crab with one large claw and one tiny claw, scuttling across a parking lot.

Ruiz and his colleagues are now studying the colorful critter in a glass case in the lab, trying to figure out where it came from and what it is. Perhaps it's an African ghost crab bought as a pet and released in the bay, Ruiz speculated.

Ten of the 100 calls turned up real Chinese mitten crabs in Maryland and Delaware, two of which showed signs of breeding. They are being kept in a freezer at the lab.


Ruiz recently thawed six of the mittens to take muscle samples from their legs to send for DNA analysis at a federal lab in Ohio. Two crabs from the bay tested earlier seemed to match Chinese mitten crabs now living in Europe.

There, the mitten crabs have behaved like cicadas since showing up in Germany in 1912. In some years, they multiply rapidly, clogging water pipes, swarming over dams and scuttling into people's homes. But then years pass when they're almost invisible, Ruiz said.

Perhaps they'll follow the same boom-and-bust pattern in the Chesapeake Bay as they did in San Francisco Bay in the 1990s. Or maybe all the mittens will die, some devoured by blue crabs. The uncertainty is typical of the mysteries surrounding exotic species, Ruiz said.

"It still surprises me how many new organisms keep showing up and how little we know about what's out there," he said.